Notes on repairing defective TiVo series 2 power supplies (the bad capacitors plague).
Series 2 power supplies often fail, I've gone through 3 of them.
The symtoms are weird boot problems, temperature warnings then failure to boot, finally failure to even show the initial grey screen. Getting down to the nub of the problem wasn't too difficult, the flakey electrolytic capacitors were the culprits. On all the ones I've worked on, the capacitors had NOT exploded yet. The TiVo seems sensitive enough to the quality of the power that it stops working before the capacitors get to the exploded stage. My solution was to replace ALL of the electrolytics on the power supply. The bad ones were labeled LTEC. Note that you will have to carefully remove the white goo put on the power supply between parts that make them vibration resistant. I just carefully cut it out with a small diagonal cutters and gently pulled the chunks out with a needle nose pliers. Here is a list of the ones I replaced:

It was probably just the large capacity ones but since they were all LTEC I replaced them all.

Notes on using a Rev C iMac (also applies to Rev A and B and probably Rev. D) with newer
versions of OSX. The boot partition on OSX has to lie within the first 8 gigs of the start of the hard drive and the maximum hard drive size is 128 gigs. (though for some
reason, while OSX only sees the first 128 gigs of the drive Linux seems to pay no attention to the 128 gig limit, more on that later). You can use a technique similar to that used by some
XServe machines to get around this. What you do is have a boot helper partition, then one large partition with OSX. The easist way to do this is to install using
XPostFacto. This is normally used to allow the installation of OSX onto
unsupported old world boxes (prior to the iMac) but supports installation and booting using a helper disk. OSX 10.3 can be installed this way with the built in CD drive but OSX 10.4
requires a DVD drive (internal only) or the dvd copied to another hard disk. I pulled my iMac apart and temporarily replaced the standard HD cable with a PC one leaving the
hard drive as master and attaching a dvd drive as slave. Next I installed OS9 creating 3 partitions, one 7 gig for OS9 (extended hfs), one 200 meg for the osxboot (extended hfs)
and the rest of the space for osx (extended hfs). After installing OS9 load up and install XPostFacto4 then run it to install OSX 10.4 from the DVD specifying the osxboot partition as the helper
disk and the DVD as the boot device. After going through all of the 10.4 installation, you'll get to the point where the machine wants to reboot. In my case the reboot FAILED! There
seems to be a bug in XPostFacto4 that writes the Open Firmware parameters wrong for the new setup. What I do at that point is to zap pram (option apple PR while powering up the
iMac) go back into os9, check the XPostFacto4 Open Firmware settings, reboot again going into Open Firmware (option apple OF) then type in the commands by hand using setenv.
This works great for me. You only have to do it once unless you zap the pram again or your motherboard pram battery needs replacing. You can do a "nvram -p" command in an OSX terminal to see your Open Firmware settings.
Here are mine after running XPostFacto then rebooting:

If you look at the settings above and compare them to the Partitions list just below, you see that boot-device describes the helper partition and boot-args describes the root partition. XPostFacto automatically sees any kernel changes and recopies them to the helper partition when you reboot (or after one boot if you've done
a software update that required a reboot). For some unknown reason XpostFacto doesn't messup the Open Firmware commands when you use it to reboot from OSX, EXCEPT for the input device! You can use the following command from terminal in OSX to fix that:

If you run OSX it seems that the system limits the hard drive to 128G. I have however successfully run larger
drives in linux. Here is the partition table from another rev C imac with a 160G drive. I copied a bunch of files
to that drive over the 128G limit and ran a filesystem check on that partition to make sure linux was actually
working properly, not just thinking (incorrectly) that it could work. This means the base hardware supports the
larger drive size. This is a rather complex partition table, the drive triple boots OS9, OSX and Linux. hda13 is
an xfs partition that spans across the 128G "barrier".